Circuit arrangement



Jan. 3, 1933. c. s. FRANKLIN ET AL 1,893,136

CIRCUIT ARRANGEMENT Filed Sept. 28, 1927 INVENTOR (names a. FRANKLIN BY ERNEST GREEN m c 664W AT RNEY Patented Jan. 3, 1933 UNETED STATES PATENT OFFICE 1 CHARLES SAMUEL FRANKLIN, OF BUCKHURST HILL, AND "ER-NEST GREEN, OF HENDON,

LONDON, ENGLAND, ASSIGNORS TO RADIO GDRPORATION OF AMERICA, A CORPORA- TION OF DELAWARE Application filed September 28, 1927, Serial No.

This invention relates to electrical energy transferring, transforming, coupling and the like devices, and more particularly to such devices for use in high frequency circuits, such as radio circuits.

In many cases, for example, in feeders for supplying high frequency energy to the aerials of an aerial system, it is desirable that the coupling or the like device for transferring energy from the feeders shall impose a certain specified efiective load, generally that of a non-inductive resistance equivalent to the surge impedance of the feeder, upon the said feeder. It has been usual toemploy air core magnetic transformers, as such coupling devices, but such transformers are not well adapted for this purpose, since they require to be compensated for the effects of magnetic leakage and reactive loads.

According to this invention an energy transferring, transforming, coupling or the like device, for use in high frequency circuits, comprises a shunt and/or series reactance or reactances inserted between the feeder and the actual load, whereby the effective load upon the said feeder may be given the required character.

The reactance or reactances may be formed of either lumped or distributed inductances and capacities.

The invention is illustrated in the accompanying drawing in which Fig. 1 shows diagrammatically one form of the invention;

Fig. 2 shows diagrammatically a second form thereof, and

Fig. 3 shows diagrammatically the invention as arranged to feed current to a plurality of aerials.

Figure 4c shows diagrammatically another form of the invention.

Referring to Figure 1, a coupling or the like device comprises an inductance L in series with, and a capacity C in shunt to, the

feeder. If it be desired to step-up the output resistance to a higher value, the feeder should be connected to the terminals X, Y, which therefore become the output of the line and the input or primary terminals of the trans- 0 formation, while the terminals A, B, consti- CIRCUI'I ARRANGEMENT 222,602, and in Great Britain October 2, 1926.

tute the output or secondary terminals of the transformation. Conversely, if it be desired to step down the output resistance, the feeder should be connected to the terminals A, B, which thus become the input or primary terminals.

To take a numerical example, if the load on the secondary is a resistance R- and a primary load of 2H is required, then the inductance L should have a reactance of R ohms, and the capacity a reactance of QR ohms at the frequency employed.

In the modification illustrated in Figure 2, the capacity C is connected in series with the feeder and the inductance L in shunt there to. In such an arrangement, for the same conditions of load and desired load as in the previous numerical example, the reactance of the capacity should be It ohms and that of the inductance 2R ohms.

lVhere the secondary load is reactive as well as resistant, the value of the inductance and/or capacity may be adjusted to compensate for this.

A particular example of the use of such a coupling device arises in a system of high frequency power distribution, for example, for feeding a plurality of aerials in anaerial system. Such a system may comprise a main section of feeder leading from a source of high frequency energy to a coupling device whose secondary feeds two further sections of feeder in parallel. Each further section of feeder may similarly supply through a coupling device two more sections of feeder, each of which supplies, through a yet further coupling device, an aerial. In order that stationary waves and consequent excessive losses and voltage stresses maybe prevented, it is necessary to make the effective terminal load on any section of feeder equal to the surge impedance of that section which is practically a pure resistance. The coupling devices hereinbefore described provide a convenient means of effecting this. For example, if the feeder has a surge impedance of R throughout and the output loads are correct, the coupling device at each junction point will be required to step-up the load from A R to R Figure 3 illustrates an embodiment in which a coupling device according to the present invention is provided in such a system of high frequency power distribution for feeding a plurality of aerials. Referring to is clearly reversible and may thus be employed for collecting energy from a plurality of receiving aerials.

If desired the coupling device may comprise a substantially uniform length of feeder, an appreciable fraction of a wave length long inserted in series between a feeder and its load, and so adjusted as to give an effectiveload of the required character upon the said feeder. If the surge impedance of a length of feeder is not equal to the load at the output end thereof, stationary waves of voltage and current occur in the said length,so that the equivalent impedance of the said length with its load varies at different points along the said length, and this phenomenon is utilized in the present construction by making the inserted length of feeder of such characteristics that the-required'load transformation is effected. For example if R is thesurg'e impedance ofthe length of feeder and 2R the terminal load, the equivalent impedance of the load and feeder at a distance of one quarter wave length from the load is a noninductive resistance of %,R.,; that is to say, a load of 2R is effectively transformed into one of R.,. In general, if R is the load resistance and R the required effective resistance, a quarter wave length of feeder of surgeimpedance is inserted as a coupling device.

It will be apparent that any type ofload may be thus transformed into any other type.

If desired, the inserted length of cable may be replaced by an artificial line.

Constructions in which the coupling device comprises an inserted cable or artificial line may be employed conveniently inaerial feeder systems such as that already described herein. For example, in the said described system in which each coupling device is required to step-up a load from R to R the said coupling device may comprise a length of cable or artificial line, one quarter 0 a wave length long and of surge impedance Having now particularly described and ascertained thenature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

1. An arrangement for matching the impedance of branched high frequency transmission lines comprising a first transmission line, other transmission lines connected in parallel, and means for coupling the first transmission line to the parallel connected transmission lines comprising a reactance of one sign connected in series with, the first line, and a reactance of opposite sign con nected in shunt across the first line. v

2. An arrangement for matching the impedance of branched high frequency transmission lines comprising a first transmission line, other parallel connected transmission lines, and means coupling the first transmission line to the parallel connected transmission lines comprising a reactance of one sign connected in series with the first transmission line, and a reactance of opposite sign connected across the first transmission line between said transmission line and the aforesaid series reactance.

8. An arrangement for matching the impedance of branched high frequency transmission lines comprising a first transmission line, other parallel connected transmission lines, and means coupling the first transmission line to the parallel connected transmission lines comprising a reactance of one sign connected in series with the first transmission line, and a reactance of opposite sign connected across the first transmission line between said transmission hue and the aforethe aforesaid reactances being equal to the surge impedance of the other transmission lines connected in parallel.

CHARLES SAMUELFRANKLIN. ERNEST GREEN. 

